In December 2019, I purchased a Mac Mini computer and connected a 42″ Samsung display using the HDMI port on the computer. It worked fine through July 2020 when I updated to Catalina. After upgrading to Catalina, the display would intermittently indicate that there was no signal from the computer, and the computer would not recognize that there was a display attached. [Read More]

In November when I upgraded to Big Sur, I hoped that the intermittent video issues would have been resolved. I also had the computer serviced and the main logic board was replaced. Initially it seemed like Big Sur and/or the repair resolved the video problems. However, they are persisting.

Known Issue

In researching the problem, I’m finding others are having HDMI issues as well. This is apparently a known issue, and Apple has two support documents with long lists of suggestions to help resolve the problem. The first document addresses how to correctly connect HDMI displays. [View] The second document covers general video issues on external displays. [View]

Some Common Fixes

Here are some of the methods I’ve used that seem to help make the external display work again:

  • Holding command + option + p + r when starting would help reset the computer’s default firmware settings. That sometimes worked to fix the problem.
  • Turning off the computer and display, then starting up again can help.
  • Disconnecting the display, and then connecting again can help.

Note: Sometimes a Samsung TV display will automatically configure itself incorrectly, and set to 30 frames per second, so the mouse movement is very slow to respond. To confirm the frame rate, press INFO on your Samsung remote. When configured properly, you should see 60 fps as the frame rate.

Conclusion

For about 10 years or longer, there has been a 100% success rate using HDMI displays plunged into most computers. Sometimes the image size needs to be adjusted, but the connection issues described above don’t seem to plague Windows computers. It’s unfortunate that used Windows computers costing $100 to $200 work fine with HDMI connected displays, but a high-end brand new Mac Mini costing over $2,000 has ongoing display issues. Hopefully Apple will get this problem resolved soon.

Testing

  • 20 Dec 2020 at 5:37 AM. After repeatedly having issues using the built-in HDMI port on my Mac Mini, I decided to use an inexpensive USB C Thunderbolt to HDMI cable. So far, this seems to have resolved the issue. Note that the main logic board on the Mac Mini had been replaced and that still didn’t fix the erratic HDMI problems.
  • 19 Dec 2020 at 9:52 AM. With a Mac Mini (2018) exhibiting HDMI issues, turning the display off and on did not help. Unplugging the video cable didn’t help. Starting with the display off or on did not help. Only holding command + option + p + r when starting helped restore the video. Then it worked fine. The video had been working fine previously, but for some reason stopped. Note that when the Samsun TV detects the signal again, it perceives the computer as an unknown device and goes through the device detection process again. It’s best to wait until it completed, then go into manual remote control configuration, then exit the setup.

Alternatives

As an alternative to the above efforts, it may work better to use a high-quality dock with HDMI output from USB C Thunderbolt such as the following.

  • CalDigit TS3 Plus Thunderbolt 3 Dock ($220) [View/Buy]
  • CalDigit USB-C Gen2 10Gb/s SOHO Dock ($100) [View/Buy]
  • CalDigit Thunderbolt 3 Mini Dock ($130) [View/Buy]

A lower priced option would be a USB C to HDMI adapter available for $10 to $20 on Amazon. [View/Buy]